Doctor mechanism for rolls and cylinders



June 235-1942. F. w. LODDING DOG TOR MECHANISM FOR ROLLS AND CYLINDERS 2 Sheets-Sheet l I INVENTOR FiledNov. 8, 1938 f; z/eric/r "(Lodz/ 17 ATTORNEY Patented June 23, 1942 UNITED STATES PATENT 1 OFFICE- oc'roa Macmmsri FOR aoLLs AND omens 3 Claims.

The present invention relates to devices known in the paper making art as doctors or scrapers, such devices being customarily employed in connection with rotating calender rolls, drier cylinders and the like, for the purpose of cleaning the surfaces of such rolls and cylinders.

In my'patent, No. 2,117,032, issued May 10, 1938, there is shown and described a doctor mechanism of the above indicated type, characterized by the provision of a thin flexible doctor blade carried by a pivoted holder, with a pressure applying member engaging the surface of the blade intermediate its edges. In operation, the holder is adapted to apply pressure between the edges of the blade, through the pressureplate, with the blade being practically self aligning, due to the fact that its entire surface is substanface of the 'roll I.

tially unconfined except along its edges, and

material into engagement withthe rotating sur- The blade 4 is made of any suitable thin-flexible material, such as steel or brass, as indicated in Fig. 3, or the blade may beformed of a suitable synthetic composition,-such as Bakelite, as indicated in Fig. 4. The blade 4 is partially received in a slot 5 extending longitudinally of the holder 2, anda pressure plate 6 cooperates with the blade 4 in retaining it in the holder slot 5, as well as in applying pressure thereto.

. As best shown in Fig. 3, the holder slot 5 provides a flat seat I, along its under side for receivslot provides a contractedportion III of suflicient width to freely receive the pressure applying plate aforementioned patent is entirely satisfactory in operation, theobject of the present invention is to provide certain improvements in the above described patented construction, as regards the manner of retaining the doctor blade in its holder, so as to permit ready withdrawal'thereof for thpurposes of replacement. A further advantage inherent in the present construction is that'while the doctor blade is freely supported between its edges, the angle of the blade with its holder, will not change when the blade is lifted from the surface being doctored. I

The above and other advantageous features of the invention will hereinafter more fully appear from the following description, with reference to the accompanying drawings, in which:

Fig. 4 is a sectional view similar to Fig.

showing a different type of blade mounted in the holder.

Fig. 5 is a plan.view,-illustrating the manner in which the blade is withdrawn from the holder.

Referring to the drawings, a portion of the surface of a roll or cylinder is indicated at I, and

the blade 4 carrying the lugs 8. For the pur-' a holder 2 is carried by an arm 3' pivotally mounted with respect to the roll. Thus. the

holder! is turnable about the pivotal axis of the' 6. The inner edge of the pressure plate 6 is secured within the slot portion," by pins II, which pass freely through openingsta in the plate. The pins II thus serve to hold the plate 6 within the slot, although permitting a certain amount of play of the plate between opposed walls of the slot.

The plate 6 extends beyond a lip 51;, formed pose of holding the blade 4 in position, the plate 6 provides punched-out tongues l2 extending each tongue I2 has a length several times the width of a lug 8. Therefore, when it is desired to remove a blade 4 from its holder 2, it is only necessary to remove pne cotter pin I3 and then shift the blade 4 endwise within the holder a distance equal to substantially one half the length of a tongue I2 on the plate 6. The whole blade 4 may then be withdrawn from the holder 2 by moving it at-right angles to the axis of the roll I, it being noted that the thickness of a lug 8 is less than the distance between the plate 6 and the edge of the blade seat I.

When inserting a new doctor blade 4 in place I2 correof a worn out blade, it is only necessary to offset the blade slightly with respect to the ends of the holder 2, as indicated in Fig. 5, so that the lugs 8 will clear the fingers I! as the'blade is pushed into the slot 5. When the inner edge of the blade 4 engages the inclined surface 9, it is only necessary to shift the blade longitudinally of the slot until its end engages the cotter pin l3 that has been left in the holder 2. This insures registration of the lugs 8 with the fingers l2, after which.

:Fig. 2. This yielding of the blade in response to pressure applied by the plate 8 ma direction opposite to the reactions set up along the edges of the blade, results in a most eifective-application of the blade to thesurface being doctored. In fact, the blade is practically self alining, since the entire upper surface of the blad is substantially unconfined, except alongits edges and zone of pressure, as applied by the plate 6.

Should the holder be turned to lift the blade 4 away from the surface of the will, as indicated in dotted lines in fig. 2, the angle of the blade with respect to the slot 5, remains substantially unchanged, due to the fact that the surfaces overhangs the blade seat 1. Therefore, the blade its holder, will not change when the blade is lifted from the surface being doctored. 1

I claim:

I 1. A doctor for rolls and cylinders comprising a pivotally mounted holder having a slot therein, a thin flexible blade having one edge thereof seated within said slot and providing a projection near said edge extending upwardly from the free surface of the blade and of less thickness than the entrance to said slot, a pressure plate overlying said blade within said slot, means for holding said pressure plate within said slot, with an edge of said plate extending beyond said slot to bear on said blade and providing a projection, intermediateits edgesand extending downwardly towards said blade, for engaging said blade projection within said slot to prevent removal of said blade from the slot in the direction of the blade width, shifting of said blade lengthwise of the slot serving to disengage said projections and thereby permit removal of the blade from'the holder by passage of said blade projection through the slot entrance.

2. A doctor for rolls and cylinders comprising a pivotally mounted holder having a slotxtherein, a thin flexible blade having one edge thereof seated within said slot and providing a projection near said edge extending upwardly from the free surface of the blade and-of less thickness than the entrance to said slot, a pressure plate overlying said blade within said slot, means for when freed from the roll, will not tend to sag, as

would occur if it were not for the inclination of the surface '9. As a result, when the blade 4 is reapplied tothe surface being doctored, it will engage this surface at the sameangle as before,

which angle is always chosen as best suited for the purposes oi doctoring the rotating surface.

. The maintenance of the original angle when the blade is reapplied is of importance when doctoring rolls or. cylinders covered with a yleldable' material, such as rubber, for should the angle of the blade change materially, its edge would dig" into the roll covering, when again engaging the rotating surface.

Referring now to Fig. 4, the doctor bladed is shown as being composed 01' a composition, such as Bakelite, so that the blade la is considerably thicker than the metallic blade 4. However, the

sameholder '2 is adapted to receive the thicker blade in, due to the fact that the slot 5 is sufliciently wide to permit the plate 6 to engage the blade do at a somewhat lower angle than as shown present invention there is provided an improved doctor mechanism for rolls and cylinders, characterized by the provision of means for retaining the doctor blade in its holder, so ,as to permit ready withdrawal thereof for purposes of replacement, with thejrelation between the parts being such as to insure that the angle of the blade with holding said pressure plate within said slot, with an edge of said plate, extending beyond said slot to bear on said blade at an angle thereto, and providing a projection extending downwardly toward said blade and of greater width than saidv blade projection but ofless length than said slot for engaging said blade projection withinthe angle between said blade and plate, to prevent removal of said blade from the slot in the direction of the blade width, shifting of said blade lengthwise of the slot for a distance less than the width of the plate projection serving to disengage said projections and thereby permit removal of the blade from the holder by passage of said blade projection through the slot entrance.

3. A doctor for rolls and cylinders comprising a pivotally mounted holder providing a slot with ofiset seats; a thin flexible blade having one edge portion engaging one slot seat of said holder and,

providing a projection extending upwardly into the space betweenvsaid seats, with said projection being of less thickness than the entrance to said slot, aplate overlying said blade within the slot, means for holding said plate within said slot with one edge bearing on the second slot seat and its other edge bearing on said blade at an angle thereto, with a portion of said plate intermediate its edges being deflected downwardly into the angle between said plate and blade ior a distance greater than the widthof said blade promovement of said blade in said slot in a direction at right angles to the pivotal axis ofsaid holder, while permitting its endwise shifting in said holder to disengage its projection from said plate, preparatory to withdrawal of the blade, by passage of its projectionthrough said slot entrance.

FREDERICK W. LODDING. 

